In the semiconductor integrated circuit (IC) industry, technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. In the course of IC evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased as a result of decreasing minimum feature size or geometry sizes (i.e., the smallest component (or line) that can be created using a fabrication process). Such scaling down has also increased the complexity of IC processing and manufacturing.
One type of feature that may be part of an integrated circuit is a Magnetic Tunnel Junction (MTJ). An MTJ is a device that changes its resistive state based on the state of magnetic materials within the device. An MTJ device includes a thin insulating layer between two ferromagnetic layers. One magnetic layer may be referred to as the reference layer. The other magnetic layer may be referred to as the free layer. The magnetic moment of the reference layer generally maintains the same direction. Conversely, through application of a voltage across the junction, the direction of the magnetic moment of the free layer can be reversed. When the direction of the magnetic moment of both the free layer and the reference layer are the same, electrons can more easily tunnel through the thin insulating layer. In this state, the junction has a relatively low resistivity.
Through application of a voltage with the opposite polarity, the magnetic moment of the free layer can be switched to oppose the direction of the magnetic moment of the reference layer. In this state, it is more difficult for electrons to tunnel through the insulating layer, causing the junction to have a relatively high resistivity. The different resistive states can be used to store logical values. Improvements are desired in this field of endeavor.